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KEMBIO2 > Proficiency Exam > Flashcards

Proficiency Exam Flashcards

1
Q

What is the simplest form of monosaccharide?

A

triose

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2
Q

What are the two trioses? Differentiate.

A

Glyceraldehyde - simplest aldose
Dihydroxyacetone - simplest ketone

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3
Q

What forms upon the reaction of an aldehyde with an alcohol? Draw and explain the mechanism.

A

A hemiacetal.

1.) The electrophilic oxygen in the alcohol group attacks the electrophilic carbonyl carbon.
2.) Upon the nucleophilic attack of the carbonyl carbon, electrons from the pi bond move towards the oxygen, and will form a negative charge.
3) The oxygen from the R-OH that attached to the carbonyl will have a positive charge.
4.) The intermediate is formed (which is unstable since there are negative and positive charges in the molecule).
5.) There will be a proton transfer (from the positively charged O to the negatively charged O).
6.) The hemiacetal is now formed.

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4
Q

A six-membered ring is called?

A

pyranose

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5
Q

a five-membered ring is called?

A

furanose

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6
Q

Cyclization from C1 to C5 of an aldohexose or C1 to C4 of an aldopentose forms a?

A

Cyclic hemiacetal

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7
Q

The monosaccharides can undergo interconversion between alpha and beta forms, using the open-chin structure as an intermediate. What is the process called? What do you call the enzymes that catalyze the reaction?

A

Mutarotation; Mutarotases

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8
Q

Sketch the Fischer and Haworth projections (pyranose and furanose form) of the following compounds:

D-xylose
D-arabinose
D-glucose
D-psicose

A

Answer on paper

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9
Q

What is the relationship of D-gulose and D-glucose in terms of stereochemistry?

A

diastereomers

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10
Q

[You can memorize the aldohexoses by hand]. Give all the C2 epimers.

A

D-Allose and D-Altrose
D-glucose an D-mannose
D-gulose and D-idose
D-galactose an D-talose

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11
Q

True or False. Only the furanose form is possible for ketopentoses.

A

True

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12
Q

Cyclization using C2 to C5 results into?

A

Hemiketal formation

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13
Q

In the conversion of Fischer projection to Haworth projection, what becomes the anomeric carbon?

A

The C1

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14
Q

Differentiate the alpha and beta anomers?

A

beta = cis
alpha = trans

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15
Q

Differentiate the configurational isomers

A

Enantiomers = nonsuperimposable mirror images
Diastereomers = nonsuperimposable, non-mirror images of one another
Anomers = stereoisomers that differ in the configuration at the anomric carbon
Epimers = stereoisomers that differ in the configuration at one carbon OTHER than the anomeric carbon

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16
Q

The resulting product when an aldose is oxidized using a mild oxidizing agent. What is being oxidized?

A

Aldonic acid, carbonyl carbon

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17
Q

The resulting product when an aldose is being oxidized using a strong oxidizing agent? What is being oxidized?

A

Aldaric aicid, C1 and C6

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18
Q

What is the product if an aldose is being oxidized at C6 via enzyme catalyzed reaction?

A

Alduronic (Uronic) Acid

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19
Q

Reduction of the carbonyl group on the sugar gives rise to the class of polyhydroxycompounds called ____?

A

Alditols

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20
Q

Elimination of water between the anomeric hydroxyl of a cyclic monosaccharide and the hydroxyl group of another compound yields to the formation of:

A

O-glycoside

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21
Q

What is sucrose?

A

The final product of photosynthesis, used as a primary energy source in many organisms. It is a disaccharide made up of alpha-glucose that is glycosidically linked to beta-fructose via alpha 1-2 glycosidic bond

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22
Q

A major animal energy source that is connecte via beta (1>4) glycosidic bond between glucose and galactose

A

Lactose

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23
Q

A major circulatory sugar in insects; use for energy. It is conneected via alpha (1>1) glycosidic bond between glucose and glucose

A

alpha-alpha trehalose

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24
Q

The dimer derived from the starch and glycogen polymers. It is an alpha (1>4) glycosidic bond between two units of glucose

A

maltose

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25
Q

The dimer of a cellulose polymer. It is connected via beta (1>4) glycosidic bond between two glucose units

A

cellobiose

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26
Q

A constituent of plant glycosides and some polysaccharides. It is connected via beta (1>6) glycosidic bond between two units of glucose

A

gentiobiose

27
Q

What are homopolysaccharides?

A

a polysaccharide that contains only one kind of monosaccharide.

28
Q

What are heteropolysaccharides?

A

A polysaccharide that is made up of several monosaccharides

29
Q

what are the storage molecules?

A

starch and glycogen

30
Q

what are the storage polysaccharides?

A

amylose and amylopectin

31
Q

difference between starch and glycogen

A

starch = energy storage in plants
glycogen = energy storage in animals

32
Q

differentiate the structure of amylose and amylopectin

A

amylose = continuous, unbranched chains of up to 4000 alpha D-glucose units joined by alpha (1>4) glycosidic bonds

amylopectin = highly branched polymer consisting of 2430 units of D-glucose joined by alpha (1>4) glycosidic bonds and branches created by alpha (1>6) glycosidic bonds

33
Q

explain the structure of glycogen

A

-it constitutes up to 10% of liver mass and 1-2% of muscle mass

-alpha (1>6) branches for every 8-12 residues

-gives red-violet color with iodine

34
Q

Draw the structure of galacturonic acid

A

.

35
Q

When an aldose is being oxidized using a mild oxidizing agent, the carbonyl carbon becomes a COOH, leading to the formation of aldonic acid. Aldonic acid is said to have an equilibrium with?

A

Lactones (cyclic carboxylic esters)

36
Q

Why is it that humans, even if they are starving, cannot utilize enormous quantities of glucose in the form of cellulose (i.e., why can’t humans gain energy if they eat plants?)

A

Because humans do not have enzymes that can catalyze the cleavage between the beta-(1>4)-glycosidic linkage

37
Q

What are the structural molecules

A

Chitin and cellulose0

38
Q

It is the major structural component of the exoskeletons of invertebrates, such as insects, crustaceans, and also occurs on the cell walls of fungi, algae, and yeasts. It is joined by beta-(1>4) glycosidic bond of N-acetyl-beta-D-glucosamine

A

chitin

39
Q

These sugars are formed by mild reduction of sugars

A

sugar alcohols

40
Q

Formerly called as mucopolysaccharides

A

glycosaminoglycans

41
Q

Chondroitin sulfates, keratan sulfates of connective tissues, dermatan sulfates of skin, and hyaluronic acid are polymers of repeating disaccharide units of?

A

N-acetylgalactosamine

42
Q

Draw the structure of beta-D-galactosamine

A

.

43
Q

These are monosaccharides with one or more hydroxyl groups replaced by hydrogens

A

Deoxy sugars

44
Q

The ribose moeity of nucleotides such as ATP and GTP is phosphorylated at what position

A

5’ position

45
Q

an enzyme that catalyzes the hydrolysis of alpha-(1>4)-glycosidic bonds

A

amylases

46
Q

an exoglycosidase and cleaves the alpha-(1>4) linkages from the nonreducing end of the polymer

A

beta-amylase

47
Q

an endoglycosidase and hydrolyzes the alpha-(1>4)-glycosidic linkages along the chain to produce glucose and maltose

A

alpha-amylase

48
Q

catalyze the hydrolysis of alpha-(1>6)-glycosidic bonds

A

debranching enzymes

49
Q

Formed by bacteria that are components of dental plaque

A

dextrans

50
Q

These are found in cell walls of nearly all plants. It is the major structural component of plants, especially wood and fibers.
-most abundant natural polymer

A

cellulose

51
Q

almost a pure cellulose

A

cotton

52
Q

Explain the structure of cellulose

A

-a linear polymer of approximately 2800 D-glucose units per molecule joined by beta-(1>4)-glycosidic bonds
-fully extended conformation with alternating 180 deg flips of glucose units

53
Q

A polymer of D-galacturonic acid joined by alpha-(1>4)-glycosidic bonds

A

Pectin

54
Q

These are polysaccharides based on a repeating disaccharide unit where one of the monomers is an amino sugar and the other has a negative charge due to a sulfate or carboxylate group

A

glycosaminoglycans

55
Q

a natural coagulant that has a structure of D-glucuronic acid-2-alpha-(1-4)-N-sulfo-D-glucosamine-6-sulfate

A

heparin

56
Q

a component of vitreous humor of the eye and the lubricating fluid of joints and has a structure of D-glucuronic acid-beta(1>3)-N-acetyl-D-glucosamine

A

hyaluronic acid

57
Q

components of tendons, cartilage, and other connective tissues

A

chondroitin sulfate and keratan sulfate

58
Q

Component of the extracellular matrix of skin

A

dermatan sulfate

59
Q

structure of heparin

A

D-glucuronic acid-2-sulfate-alpha-(1>4)-N-sulfo-D-glucosamine-6-sulfate

60
Q

structure of hyaluronic acid

A

D-glucuronic acid-beta-(1>3)-N-acetyl-D-glucosamine

61
Q

structure of chondroitin sulfate

A

D-glucuronic acid-beta-(1>3)-N-acetyl-D-galactosamine-4-sulfate

62
Q

structure of keratan sulfate

A

D-galactose-beta-(1>4)-N-acetyl-D-glucosamine-6-sulfate

63
Q

these contain carbohydrate units covalently bonded to a polypeptide chain

A

glycoproteins

KEMBIO2 (1 decks)

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